Skpt., 1905.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



SesLweeds 



A HolidaLy Pa-per for Field 

 BotaLiiists. 



By David W. Bevan, Scarborough F.N. Society. 



II. -The Red Seaw^eeds. 



If the brown seaweeds are the g-iants of the shore, the 

 red are the fairies. These httle plants show an almost 

 endless variety of form, but they are all really very 

 much alike in build. Like all other lowly plants, the 

 seaweeds are built up entirely of cells, and it is simply 

 the grouping- of these cells, and their way of dividing, 



Fig. 1. Fig. 2. 



that determine the shape and appearance of the red 

 seaweeds. 



We have only time to glance at a few of those that 

 are pretty sure to^ turn up. One of the loveliest little 

 things for the microscope is CalUthamnion rosetim (Fig. 

 I — a). It is unfortunate that these little beauties have no 

 "common" name. Tlie botanical name means, in plain 

 English, " The bonny bush of rosy hue." It is a 

 simple row of oblong cells, with branches of the same 

 pattern coming off right and left alternately, each cell 

 of the branch again bearing a branch : — a bonny little 

 plant, only about half an inch high, at most, growing 

 often on the bare rock. Each cell contains a number 

 of round, red bodies, corresponding to- the chlorophyll 



corpuscles of the land plants. Similarly, the brown 

 seaweeds are brown because their colour-bodies are 

 brown. But they all contain chlorophyll. Put bits of 

 a red and a brown seaweed in alcohol for a few 

 minutes ; these colours are dissolved out, and the sur- 

 prising fact appears that the brown seaweeds, and the 

 red, are as green as grass. 



Another CalUthamnion {floridulum) entangles mud 

 and sand in its branches, forming dense, dark red 

 cushions up to two inches in thickness. As you wend 

 your way over these cushions, you would scarcely 

 suspect you were treading on a plant. On tearing the 

 cushion open, we find the plant is dead below, but ever 

 growing at the top — like the bog moss. 



The most delicate seaweed known to the writer, and 

 a pretty object for the microscope, is Baiigia, a single, 



unbranched filament of extreme delicacy. It grows in 

 the most reposed situations that are daily hammered by 

 the waves. How it survives — and winter is its most 

 flourishing time — is a mystery. Though it begins life 

 as a single row of cells, a transverse section taken at 

 maturity w'ould pass through four cells, and these 

 divide again to produce spores. Fig. 4 is a highly 

 magnified view of a portion of a filament, the outlines 

 only of the cells being shown. 



The Folysiphonias (Fig. 2), with their long cells 

 arranged like the staves of a barrel, and the Ceraniiums, 

 with their pretty forked and often curved tips, are 

 very common ; and they are all very beautiful under 

 the microscope. 



Fig. S. 



Fig. 6. 



The commonest i-'olysiphonia, and one which is sure 

 to be met with, grows in bushy tassels on the Knotted 

 WVack and it is as pretty as any of them. Tliey all 

 divide dichotomously, and can be recognised by the 

 lens, as each "internode" of the filament has one large, 

 central cell, and a number (varying in different species) 

 of long, narrow red cells, arranged round it (see Fig. 



Fig. 7. 



Fig. 8. 



^ — a, which is a part of Fig. 2 — a, more highly magni- 

 fied). The Ceramiums are also dichotomous, and have, 

 as a rule, curled tips. The naked eye shows they are 

 made up of alternate light and dark coloured seg- 

 ments. While all are charming, words fail to describe 

 the exquisite beauty of the Bristly Ceramium (C. cilia- 

 turn), when a small snipping is examined under either 

 low or high power (Fig. 5 — a). It grows at Scarborough 

 on the front face of the limestone platform of the 

 White Nab — a tiny plant only about one-third of an 

 inch high — along with a little Polysiphonia with only 

 four "staves" toi its "barrel." This little Ceramium is 

 easily known by its strongly-incurved tips, and by the 

 colourless hairs growing on its frond. One's first 

 impulse, on seeing this little beauty, is to call one's 

 friends and neighbours together to share one's joy. 



